Purpose of CONSOLE_REAL_OUTPUT_HANDLE macro

Question

I read wincon.h header and I found two macros:

CONSOLE_REAL_OUTPUT_HANDLE (LongToHandle(-2))

CONSOLE_REAL_INPUT_HANDLE (LongToHandle(-3))

I've searched across the internet but still didn't find answer.

What's the purpose of those macros? It seems like it's undocumented because I can't find it on MSDN.